Connecting the motor according to the star-delta 380 circuit. Star and delta connection principle

Three-phase asynchronous motors are more efficient than single-phase motors and have become much more common. Electrical devices operating on motor traction are most often equipped with three-phase electric motors.

An electric motor consists of two parts: a rotating rotor and a stationary stator. The rotor is located inside the stator. Both elements have conductive windings. The stator winding is laid in the grooves of the magnetic core maintaining a distance of 120 electrical degrees. The beginnings and ends of the windings are brought out and fixed in two rows. The contacts are marked with the letter C, each is assigned a numerical designation from 1 to 6.

The phases of the stator windings, when connected to the power supply network, are connected according to one of the following schemes:

• "triangle" (Δ);
• "star" (Y);
• combined star-delta circuit (Δ/Y).

Connection via combined scheme used for motors with power over 5 kW.

« Star" refers to the connection of all ends of the stator windings at one point. The supply is supplied to the beginning of each of them. When the windings are connected in series into a closed cell, a “ triangle" The contacts with the terminals are positioned in such a way that the rows are offset relative to each other, C1 is located opposite the C6 terminal, etc.

The supply of supply voltage from a three-phase network to the stator windings creates a rotating magnetic field that sets the rotor in motion. The torque that occurs after is not enough to start. To increase torque, additional elements are included in the network. The simplest and most common way to connect to household networks is to connect using a phase-shifting capacitor.

When supply voltage is supplied from both types of electrical networks, the rotor speed of the asynchronous motor will be almost the same. At the same time, the power in three-phase networks is higher than in similar single-phase ones. Accordingly, connecting a three-phase electric motor to a single-phase network is inevitably accompanied by a noticeable loss of power.

There are electric motors that are not initially designed to be connected to a household network. When purchasing an electric motor for domestic use, it is better to immediately look for models with a squirrel-cage rotor.

Connecting the motor with star and delta in networks with different rated voltages

In accordance with the rated supply voltage, domestically produced asynchronous three-phase motors are divided into two categories: for operation from 220/127 V and 380/220 V networks. Motors designed to operate from 220/127 V have low power - today they are used very limited.

Electric motors designed for a rated voltage of 380/220 V are widespread everywhere. Regardless of the rated voltage, when installing the motor, the rule is used: lower voltage values ​​are used when connecting in a “triangle”, high voltages are used exclusively in connections of the stator windings in a “star” configuration.
That is, the voltage in 220 V served on " triangle», 380 V- on " star", otherwise the motor will quickly burn out.

Basic specifications unit, including the recommended connection diagram and the possibility of changing it are displayed on the motor tag and its technical passport. The presence of a mark of the form Δ/Y indicates the possibility of connecting the windings with both a star and a delta. To minimize power losses that are inevitable when operating from single-phase household networks, it is better to connect a motor of this type in a triangle.

The Y sign denotes motors where the possibility of connecting to a “triangle” is not provided. IN distribution box of such models, instead of 6 contacts, there are only three; the connection of the other three is made under the body.

Three-phase connections with a rated supply voltage of 220/127 V to standard single-phase networks are performed only as a star. Connecting a unit designed for low supply voltage to a “triangle” will quickly render it unusable.

Features of the operation of an electric motor when connected in different ways

Connecting an electric motor with a “triangle” and a “star” is characterized by a certain set of advantages and disadvantages.

The star connection of the motor windings ensures a softer start. In this case, a significant loss of unit power occurs. According to this scheme, all 380V electric motors of domestic origin are also connected.

The delta connection provides an output power of up to 70% of the rated power, but the starting currents reach significant values ​​and the motor may fail. This circuit is the only correct option for connecting imported European-made electric motors designed for a rated voltage of 400/690 to Russian electrical networks.

The star-delta starting function is only used for motors marked Δ/Y, which have both connection options. The engine is started using a star connection to reduce the starting current. As the engine accelerates, it shifts into delta to get the maximum possible power output.

The use of a combined method is inevitably associated with current surges. At the moment of switching between circuits, the current supply stops, the rotor rotation speed decreases, in some cases it sharply decreases. After some time, the rotation speed is restored.

Examples of star and triangle connections in the video

Asynchronous motors have a whole range of undoubted advantages. Among the advantages of asynchronous motors, first of all, I would like to mention the high performance and reliability of their operation, the very low cost and unpretentiousness of motor repair and maintenance, as well as the ability to withstand fairly high mechanical overloads. All these advantages that they have asynchronous motors, is due to the fact that this type of engine has a very simple design. But, despite the large number of advantages, asynchronous motors also have certain negative aspects.

IN practical work It is customary to use two main methods of connecting three-phase electric motors to the electrical network. These connection methods are called: “star connection” and “delta connection”.

When a three-phase electric motor is connected using the star connection type, then the ends of the stator windings of the electric motor are connected at one point. In this case, three-phase voltage is supplied to the beginning of the windings. Below, in Figure 1, the connection diagram for a star asynchronous motor is clearly illustrated.

When a three-phase electric motor is connected using the “delta” connection type, then the stator windings of the electric motor are connected in series one after another. In this case, the beginning of the subsequent winding is connected to the end of the previous winding, and so on. Below, in Figure 2, the connection diagram of a delta asynchronous motor is clearly illustrated.

If you do not go into the theoretical and technical foundations of electrical engineering, then you can take for granted the fact that the operation of those electric motors whose windings are connected in a star configuration is softer and smoother than that of electric motors whose windings are connected in a delta configuration ". But here it is worth paying attention to the peculiarity that electric motors, the windings of which are connected in a star configuration, are not capable of developing the full power declared in the passport characteristics. In the event that the windings are connected according to the "triangle" pattern, then the electric motor operates at maximum power, which is stated in the technical data sheet, but at the same time there are very high values ​​of starting currents. If we make a comparison in terms of power, then electric motors whose windings are connected in a delta configuration are capable of delivering power one and a half times higher than those electric motors whose windings are connected in a star configuration.

Based on all of the above, in order to reduce currents during startup, it is advisable to use a combined delta-star connection of the windings. This type of connection is especially relevant for electric motors with greater power. Thus, due to the delta-star connection, the starting is initially carried out in the star configuration, and after the electric motor has gained momentum, switching is carried out in automatic delta mode.

The electric motor control circuit is shown in Figure 3.

Rice. 3 Control circuit

Another version of the electric motor control circuit is as follows (Fig. 4).

Rice. 4 Engine control circuit

The NC (normally closed) contact of time relay K1, as well as the NC contact of relay K2, in the circuit of the short-circuit starter coil, is supplied with supply voltage.

After the short-circuit starter is turned on, the normally closed short-circuit contacts disengage the circuits of the K2 starter coil (prohibition of accidental activation). The short circuit contact in the power supply circuit of the starter coil K1 closes.

When the magnetic starter K1 starts, the K1 contacts close in the power circuit of its coil. The time relay turns on at the same time, the contact of this relay K1 in the short circuit starter coil circuit opens. And in the starter coil circuit K2 it closes.

When the short circuit starter winding is disconnected, the short circuit contact in the starter coil circuit K2 will close. After the K2 starter turns on, it opens the power circuit of the short-circuit starter coil with its K2 contacts.

Three-phase supply voltage is supplied to the beginning of each of the windings W1, U1 and V1 using the power contacts of the starter K1. When the short-circuit magnetic starter is triggered, then with the help of its short-circuit contacts a short circuit is made, through which the ends of each of the electric motor windings W2, V2 and U2 are connected to each other. Thus, the motor windings are connected using a star connection.

A time relay combined with a magnetic starter K1 will operate after a certain time. This causes a shutdown magnetic starter Short circuit and simultaneous activation of magnetic starter K2. Thus, the power contacts of the starter K2 will be closed and the supply voltage will be supplied to the ends of each of the windings U2, W2 and V2 of the electric motor. In other words, the electric motor is switched on according to the “delta” connection diagram.

In order to start the electric motor using a delta-star connection, various manufacturers produce special starting relays. These relays can have various names, for example, “start-delta” relay or “start time relay”, as well as some others. But the purpose of all these relays is the same.

Typical scheme, made with a time relay designed for starting, that is, a delta-star relay, to control the starting of a three-phase asynchronous type electric motor is shown in Figure 5.

Fig. 5 Typical circuit with a starting time relay (star/delta relay) for controlling the start of a three-phase asynchronous motor.

So, let's summarize all of the above. In order to reduce starting currents, starting the electric motor is required in a certain sequence, namely:

1. first, the electric motor is started at low speeds connected in a star configuration;
2. then the electric motor is connected in a delta pattern.

The initial start according to the "triangle" circuit will create the maximum torque, and the subsequent connection according to the "star" circuit (for which the starting torque is 2 times less) with continued operation in the nominal mode, when the engine has "picked up speed", there will be a switch to the "delta" connection circuit "in automatic mode. But do not forget about the load that is created on the shaft before starting, since the torque is weakened when connecting in a star configuration. For this reason, it is unlikely that this starting method will be suitable for electric motors with high loads, since they may then lose their functionality.

It is a useful device that is used in many areas of human activity, from everyday life to industry. In various grinding machines, on conveyors, machine units, industrial ventilation systems and more. The electric motor has 3 outputs, so a star-delta connection can be made to a three-phase network alternating current or transformer.

Engine design

The windings are located on the stator, and the rotor is short-circuited in the form of a squirrel wheel: aluminum or copper rings at the ends are connected to each other by parallel jumpers. The stator is wound in a special way with a certain number of poles, which depends on the power parameters and the supply network. Household fans have only 2 poles, industrial traction motors have 8 or more.

Benefits of using asynchronous electric motors with a star or delta connection circuit are obvious and are as follows:

Methods for connecting to the network

Now let's try to figure out what a star and a triangle are, what is the difference between them. Asynchronous 3-phase electric motor has 3 windings, which are connected in a certain way. They can be connected both to a 380 V network and to an alternating voltage of 220 V. Therefore, the motor can be considered universal, but its performance quality directly depends on the method of connection to the network or a separate supply transformer.

For example, in acceleration mode, when it is connected in series to the motor circuit to reduce the starting voltage. A frequency converter operates on this principle, regulating the initial torque by changing the frequency, preventing power consumption from exceeding more than 10-20%. In normal starting mode, an asynchronous motor consumes up to 600% of the nominal value, which can cause automatic shutdown of the input circuit breakers.

Typically, when you open the terminal box on the motor, you will see 3 pins and an additional twist. This indicates the type of connection of the windings, which in this case is a star. By unwinding the common connection, you will get 6 pins, which are the ends and beginnings of each of the 3 windings. Therefore, it becomes possible to make a connection using a triangle diagram.

Sometimes, depending on the control method and the algorithm for generating control voltage in the drive, switching from star to delta is required. And you can do this automatically mode, for example during acceleration, so that the electric motor immediately provides high torque. This is most often used in frequency control systems where more tightly controlled motor dynamics and rotational speed control are required.

When and which scheme is best to use depends on the requirements, but each method has its own characteristics. For example, they consist in the developed and consumed power, the difference in linear and phase voltages, and, accordingly, dynamic and electrical indicators.

Basic formulas

Before you get acquainted with the features of how to connect a star-delta electric motor, it is worth remembering the basic formulas for calculating power and the ratio of voltages and currents between them. When calculating powered devices from an alternating voltage network or a separate transformer, the concept of apparent power is used. It is denoted by the capital letter S and is found as the product of the effective value of voltage and current U × I. Also, it is possible to calculate based on the EMF, at which S = E × I.

In addition to the full one, there are also:

• active;
• reactive power.

In the first case, it is denoted by the letter P = E × I × cos φ or P = U × I × cos φ. In the second case, Q = E × I × sin φ or Q = U × I × sin φ. Where in the formulas E is the electromotive force, I is the current, φ is the angle between the voltage and current created by the phase shift in the windings.

If the motor windings are identical to each other in all respects, then all types of power are determined as the product of current and voltage multiplied by 3.

Star motor connection

The most commonly used is the star connection, because in this mode the necessary power is provided and good torque on the shaft is guaranteed. But it is worth understanding that an underloaded motor in a 3-phase network will consume excess power, so it is better to use a less powerful motor or adjust the frequency of the supply transformer or drive, depending on the voltage source.

And to determine electrical parameters networks, it is necessary to use the relation √3. Initially, it should be noted that when connected in a star, the linear and phase currents are the same, and the voltage is determined by the formula U = √3 × U f. It is not difficult to find the phase voltage from it. Accordingly, powers are determined taking into account this ratio:

S = √3 × U × I

It should be remembered that if the transformer, in addition to 3 phases, also has a 4th terminal from the middle point, then it must be connected to the electric motor .

Features of using a star connection

In enterprises, and in all other areas, the main type of connection for 3-phase motors is a star, and they are powered from a common substation or a separate transformer, thus providing galvanic isolation. The connection circuit of its windings does not particularly affect the operation of the engine. If they are connected in a triangle, then the output voltage will be 1.73 times less and by connecting the motor to its windings in a delta circuit, you can achieve approximately the same torque as in normal mode.

The phase currents when connected according to a star circuit are equal, and the voltage supplied to each of the windings is 1.73 times less. The engine gains its torque over a longer period of time, but does not overheat. In this mode, motors are used on fans, pumps, augers and other units. But, if it is necessary to increase the torque and traction capacity, then it is briefly switched to a triangle.

In this case, the full mains voltage is supplied to the windings, and, consequently, an increased current, which leads to the release of additional power on the shaft and heating of the motor. The delta switching mode is used to accelerate the engine start, and therefore return the connection circuit to its original state. Long-term operation in this mode will lead to rapid failure.

How to connect a motor according to the “Star-Delta” scheme

There is plenty written about star-delta motor connection diagrams. But every article contains inaccuracies and errors. The authors simply copy from each other. I suspect that most of them have never connected a motor in their lives, and the name of the circuit for them is just geometric figures. So I decided to follow folk wisdom“if you want to do it well, do it yourself,” and write this article.

I am telling you based on my experience and understanding of the issue. As always, I will give the theory and show what it looks like in practice.

To begin with, if someone is completely out of the loop, what area of ​​knowledge is this all from? We are talking about one of the common methods of connecting a three-phase asynchronous electric motor, in which the motor windings are first connected to the supply network in a star circuit, and then in a delta circuit. In young inquisitive minds the question will immediately arise - “Why is this necessary?” OK.

Why do we need a “Star-Triangle” scheme?

The root of the problem lies in the starting currents and excessive loads that the motor experiences when power is applied directly to it. What about the engine - the entire drive grinds and shudders when starting!

IMPORTANT! If you've read this far, . There is a lot of detail about where they come from, how to recognize them, count and measure them.

This is especially critical where there is no reduction gear - a gearbox or a belt on pulleys.

This is especially important where something massive is mounted on the engine shaft - an impeller or a centrifuge.

Subscribe! It will be interesting.

This is especially significant where the engine power is more than 5 kW and the rotation speed is high (3000 rpm).

These are the pigs that don’t like being connected directly to the network

The drive is different from the engine, like a wheel is from a tire and like.

So, in order to reduce the power on the motor shaft during start-up, it is first turned on at a reduced voltage, it slowly accelerates, and then turned on at full, rated power. This is implemented not by changing the voltage with rheostats and transformers, but in a more cunning way. But in order.

“Star” and “Triangle” schemes

Any classic three-phase motor has three stator windings. They may have different configurations in space, additional conclusions, but there are three of them.

Diagram of stator windings with leads for a three-phase asynchronous motor

How to connect all these 6 pins if our power supply only has 3 phases?

In short, here is the simplest diagram:

Star-Delta control circuit with time relay. The simplest theoretical

In contacts with a time delay, everyone is constantly confused. I have it right)

You already know what KM1, KM2, KM3 are, but KA1 is a time relay with a delay when turned on. The relay can be anything, be it electronic or pneumatic, such as PVL. The main thing is that the contacts switch from the initial state after a delay time after power is applied to KA1.

You can supply power to the circuit (start the engine) by any means - even with a toggle switch, at least.

The disadvantage of this scheme is that there is a danger of conflict between KM2 and KM3. That's why I don't really like this scheme, because... it operates “on the edge”, and its failure-free operation is highly dependent on the mechanics and design of the contactors. Because of this, the contacts may burn out, or the input machine may be knocked out. Therefore, locking is required (electrical and preferably mechanical):

Practical star-delta circuit with interlocking

The blocking is implemented on NC contacts, more about this and more. A mechanical interlock is shown between the coils, not to be confused with the “Triangle” circuit!

This is a real scheme, you can apply it. If something is not clear, ask.

By the way, instead of KA1.1 you can install a NO contact with a Shutdown delay. That is, it turns on immediately after power is applied, and turns off after a while. But for this you need two separate time relays with different operating principles, which must be synchronized to guarantee a pause. This is exactly what is implemented in specialized “Star-Triangle” time relays.

Yes, one more note. Sometimes the power supply to the general contactor KM1 is turned on not directly, but through the NO contact of the “Star” KM2, then KM1 becomes self-retaining through its NO contact. This is necessary for additional testing of the functionality of the time relay KA1.

Timing diagrams of the Star-Delta circuit operation

With reference to my control circuit, contactor switching diagrams:

Star-delta control timing diagrams

Everything seems clear here, but there is one thing important note. Again. A small gap (pause) is required between the green and red areas. It may not exist (pause = 0), but these areas can overlap each other if contactors with a coil are used direct current(=24 VDC). Especially when using a reverse-connected diode (and it is required!), the turn-off time can be 7-10 times longer than the turn-on time!

What I mean is that I once suffered with such a scheme; it periodically knocked out the input machine. We installed a special relay with a pause, the problem was solved!

Real circuit example

Here real example such a circuit on an electronic time relay:

Photo of a star-delta circuit with timer control and galvanic isolation on a transformer.

From left to right in the bottom row: KM1, KM2, KM3, KA1.

And here is an example of a circuit controlled by a controller:

Star-delta, compressor, controlled by controller program

Video of how the contactors click in this circuit:

Here's how beautifully the Germans designed the circuit in their compressor:

Star-Triangle compressor circuit

There are three wires at the input of the circuit, and six at the output. Everything fits)

How to switch the engine circuit to “Star” and “Triangle” manually

If no automation is needed, and the engine operates constantly in “Star” or “Triangle”, then using an open-end wrench, you can switch the winding connection diagram manually.

Motor nameplate 220 / 380 V 0.37 kW

On the back of the boron cap, as usual, there is a diagram:

Connection diagram 220 – 380 on the engine cover

The motor was powered directly from a three-phase 380 V network through a contactor and was assembled into a “Star:

The motor terminals are connected in a star connection

Unscrew the M4 nuts, remove the jumpers and power wires:

We disassemble the circuit, remove the wires

We assemble the circuit into a triangle, for a reduced voltage of 220 V:

Assembling a triangular circuit for 220 V

The alteration was necessary due to the fact that it was necessary to change the engine rotation speed, and to do this, use a frequency converter. And frequency generators for such power are usually single-phase. As a result, let's go!

By the way, I’m planning a series of articles on frequencies, subscribe!

Features of working at Zvezda

In accordance with GOST 28173 (IEC 60034-1), motors can be operated with a voltage deviation of ± 5% or
frequency deviation ± 2%. In this case, the motor parameters may differ from the nominal ones, and the temperature rise of the windings may be 10 °C higher than the limit according to GOST 28173 (IEC 60034-1).

What am I talking about? The fact is that during startup, when the engine is running in “Star” mode, it does not work in the mode (the voltage differs by 70%!), which can lead to overheating if this lasts for a long time. Be careful to protect the engine from overheating and overload! But that's a completely different story)

Video

In a three-phase network there are usually 4 wires (3 phases and zero). There may also be a separate ground wire. But there are also ones without a neutral wire.

How to determine the voltage in your network?
Very simple. To do this, you need to measure the voltage between phases and between zero and phase.

In 220/380 V networks, the voltage between phases (U1, U2 and U3) will be equal to 380 V, and the voltage between zero and phase (U4, U5 and U6) will be equal to 220 V.
In 380/660V networks, the voltage between any phases (U1, U2 and U3) will be equal to 660V, and the voltage between zero and phase (U4, U5 and U6) will be equal to 380V.

Possible connection diagrams for electric motor windings

Asynchronous electric motors have three windings, each of which has a beginning and an end and corresponds to its own phase. Winding designation systems may vary. In modern electric motors, a system has been adopted for designating windings U, V and W, and their terminals are designated by number 1 as the beginning of the winding and by number 2 as its end, that is, the U winding has two terminals: U1 and U2, the V winding has V1 and V2, and the W winding – W1 and W2.

However, old asynchronous motors made during the Soviet era and having the old Soviet marking system are still in operation. In them, the beginnings of the windings are designated C1, C2, C3, and the ends - C4, C5, C6. This means that the first winding has terminals C1 and C4, the second - C2 and C5, and the third - C3 and C6.

The windings of three-phase electric motors can be connected in two different patterns: star (Y) or delta (Δ).

Connecting an electric motor according to a star circuit

The name of the connection diagram is due to the fact that when the windings are connected according to this diagram (see figure on the right), visually it resembles a three-rayed star.

As can be seen from the electric motor connection diagram, all three windings are connected together at one end. With this connection (220/380 V network), a voltage of 220 V is applied to each winding separately, and a voltage of 380 V is applied to two windings connected in series.

The main advantage of connecting an electric motor according to a star circuit is the small starting currents, since the supply voltage of 380 V (phase-to-phase) is consumed by 2 windings at once, in contrast to the delta circuit. But with such a connection, the power of the powered electric motor is limited (mainly for economic reasons): usually relatively weak electric motors are turned on in a star.

Connecting an electric motor according to a triangle diagram

The name of this scheme also comes from the graphic image (see right picture):

As can be seen from the electric motor connection diagram - “triangle”, the windings are connected in series to each other: the end of the first winding is connected to the beginning of the second and so on.

That is, a voltage of 380 V will be applied to each winding (when using a 220/380 V network). In this case, more current flows through the windings; motors of higher power are usually switched on in a triangle than with a star connection (from 7.5 kW and above).

Connecting the electric motor to a three-phase 380 V network

The sequence of actions is as follows:

1. First, let’s find out what voltage our network is designed for.
2. Next, we look at the plate that is on the electric motor, it may look like this (star Y / triangle Δ):

(~1.220V)

220V/380V (220/380, Δ / Y)

(~3, Y, 380V)

Motor for three-phase network
(380V / 660V (Δ / Y, 380V / 660V)

3. After identifying the network parameters and the electrical connection parameters of the electric motor (star Y / delta Δ), we proceed to the physical electrical connection electric motor.
4. To turn on a three-phase electric motor, you need to simultaneously apply voltage to all 3 phases.
Enough common reason failure of the electric motor - operation in two phases. This can happen due to a faulty starter, or due to phase imbalance (when the voltage in one of the phases is much less than in the other two).
There are 2 ways to connect the electric motor:
- usage circuit breaker or motor protection circuit breaker

When turned on, these devices supply voltage to all 3 phases at once. We recommend installing a motor protection circuit breaker of the MS series, since it can be adjusted exactly to the operating current of the electric motor, and it will sensitively monitor its increase in the event of an overload. This device at the moment of starting makes it possible to work for some time at an increased (starting) current without turning off the engine.
A conventional circuit breaker must be installed in excess of the rated current of the electric motor, taking into account the starting current (2-3 times higher than the rated current).
Such a machine can turn off the engine only in the event of a short circuit or jamming, which often does not provide the necessary protection.

Using the starter

The starter is an electromechanical contactor that closes each phase with the corresponding motor winding.
The contactor mechanism is driven by an electromagnet (solenoid).

Electromagnetic starter device:

The magnetic starter is quite simple and consists of the following parts:

(1) Electromagnet coil
(2) Spring
(3) Movable frame with contacts (4) for connecting network power (or windings)
(5) Fixed contacts for connecting electric motor windings (power supply).

When power is supplied to the coil, the frame (3) with contacts (4) lowers and closes its contacts to the corresponding fixed contacts (5).

Typical diagram for connecting an electric motor using a starter:

When choosing a starter, you should pay attention to the supply voltage of the magnetic starter coil and buy it in accordance with the possibility of connecting to a specific network (for example, if you have only 3 wires and a 380 V network, then the coil should be taken at 380 V, if you have network is 220/380 V, then the coil can be 220 V).

5. Check that the shaft is spinning in the right direction.
If you need to change the direction of rotation of the electric motor shaft, then you just need to swap any 2 phases. This is especially important when powering centrifugal electric pumps that have a strictly defined direction of rotation of the impeller.

How to connect a float switch to a three-phase pump

From all of the above, it becomes clear that to control a three-phase pump motor in automatic mode using a float switch, you CANNOT simply break one phase, as is done with single-phase motors in a single-phase network.

The easiest way is to use a magnetic starter for automation.
In this case, it is enough to integrate a float switch in series into the power supply circuit of the starter coil. When the float closes the circuit, the starter coil circuit will close and the electric motor will turn on; when it opens, the power to the electric motor will be turned off.

Connecting the electric motor to a single-phase 220 V network

Usually, to connect to a single-phase 220V network, special motors are used that are designed to connect specifically to such a network, and problems with their power supply do not arise, because this simply requires inserting a plug (most household pumps are equipped with a standard Schuko plug) into the socket

Sometimes it is necessary to connect a three-phase electric motor to a 220 V network (if, for example, it is not possible to install a three-phase network).

The maximum possible power of an electric motor that can be connected to a single-phase 220 V network is 2.2 kW.

The easiest way is to connect the electric motor through a frequency converter designed for power supply from a 220 V network.

It should be remembered that the 220 V frequency converter produces 3 phases of 220 V at the output. That is, you can only connect to it an electric motor that has a supply voltage of 220 V three-phase network (usually these are motors with six contacts in a junction box, the windings of which can be connected both in star and triangle). In this case, it is necessary to connect the windings in a triangle.

It is possible to connect a three-phase electric motor to a 220 V network using a capacitor even more simply, but such a connection will lead to a loss of motor power of approximately 30%. The third winding is powered through a capacitor from any other.

We will not consider this type of connection, since this method does not work normally with pumps (either the engine does not start when starting, or the electric motor overheats due to a decrease in power).

Using a frequency converter

Currently, everyone has quite actively begun to use frequency converters to control the rotational speed (RPM) of an electric motor.

This allows you not only to save energy (for example, when using frequency control of pumps for water supply), but also to control the supply of positive displacement pumps, turning them into dosing ones (any pumps of a positive displacement principle).

But very often when using frequency converters, they do not pay attention to some of the nuances of their use:

Frequency adjustment, without modifying the electric motor, is possible within the frequency adjustment range +/- 30% of the operating one (50 Hz),
- when the rotation speed increases above 65 Hz, it is necessary to replace the bearings with reinforced ones (now with the help of a state of emergency it is possible to increase the current frequency to 400 Hz, ordinary bearings simply fall apart at such speeds),
- when the rotation speed decreases, the built-in fan of the electric motor begins to work inefficiently, which leads to overheating of the windings.

Due to the fact that they do not pay attention to such “little things” when designing installations, very often electric motors fail.

To operate at low frequencies, it is MANDATORY to install an additional forced cooling fan for the electric motor.

A forced cooling fan is installed instead of the fan cover (see photo). In this case, even when the main engine shaft speed decreases,
An additional fan will ensure reliable cooling of the electric motor.

We have extensive experience in retrofitting electric motors to operate at low frequencies.
In the photo you can see screw pumps with additional fans on electric motors.

These pumps are used as dosing pumps in food production.

We hope that this article will help you correctly connect the electric motor to the network yourself (or at least understand that this is not an electrician, but a “general specialist”).

Technical Director
LLC "Pumps Ampika"
Moiseev Yuri.